Aim for the head (shoots the chest) no the head! (shoots the futa penis) NO THE OTHER OTHER HEAD! (shoots your head).....
-Game over-
I mean, the knife works pretty well too. Chest shots are guaranteed damage, headshots if you line it are pretty much 2x damage all around. takes average 2-3 for standard female futa kills to head, 2-3 knives for kills as well.
so by logic the knife is the equal to a headshot.
7-9 for the twin blade chicks (headshots),7-9 knives takedown. unless somethings changed it seems pretty equal across the board.
minus the facehugger crawlers and ceiling grapplers... those two you honestly cannot knife or its extremely hard to.
edit: Honestly you can defeat the boss of the demo by standing in the middle of them... or at least to a degree their melee strike doesnt hit in the center so you just walk there and no hits. continue shooting/stabbing etc.